The field of this invention relates to techniques for improving the performance of fishing and drilling jars in deviated well bore conditions.
The problem addressed by the method of the present invention is illustrated in FIG. 1. Referring to FIG. 1 a deviated well bore 10 is illustrated. The deviated well bore 10 has a 90xc2x0 bend 12. Further down in the well bore a stuck object or xe2x80x9cfishxe2x80x9d 14 is located. The fish 14 could be a liner string or a downhole tool. A jar 16 is secured to a tubing string 18 for ultimate attachment to the fish 14. These jars require a significant amount of overpull and are known for their ability to deliver high impact blows to a stuck object. The frequency of the blows is quite low. However the magnitude of the force delivered is a multiple of the overpull force applied which can be in the order of tens of thousands of pounds or more. FIG. 1 readily illustrates the problem when attempting to use this type of jar in the deviated well bore 10. The tubing string 18 makes contact with the wall 20 of the well bore 10. This impedes the degree of overpull that can be applied to the jar 16 and thus moderates the applied impact load to the fish 14 to free it. In essence the frictional forces at the bend 12 acting on the tubing string 18 limit the amount of tension that can be applied to the string 18 which is transmitted to the jar 16.
One approach in the prior art has been to work the tubing string 18 up and down with the draw works at the surface. This technique has had very limited success.
Various high frequency vibratory devices have been used in tandem with rotating bits to promote drilling operations. Such techniques are illustrated in U.S. Pat. Nos. 4,462,471; 4,958,691; 5,156,223. Such high frequency vibratory tools have also been used to release stuck objects in the well bore by being attached directly to the stuck object. When fluid is pumped through such tools vibration ensues and the vibration hopefully frees the stuck object such as a liner string.
The object of the present invention is to alleviate the problems for applications of fishing and drilling jars which rely on significant amounts of applied overpull in deviated or horizontal well bores. Thus the objective of the present invention is to be able to ensure transmission of the applied overpull force at the surface to the jar which is in the deviated or horizontal segment of the well bore. Those skilled in art will readily appreciate how the objective of the method of the present invention is accomplished by a review of the preferred embodiment which appears below.
A method for using fishing and drilling jars which require high applied tensile loads in deviated or horizontal well bores is described. The method involves the placement of the string of high frequency vibratory devices that are triggered by flow therethrough. These vibratory devices are placed in the region of the bend or deviation in the well bore. The vibratory forces are applied coincidently with the tensile overpull force so as to fully utilize the applied overpull force at the surface down hole at the jar which is attached to the fish.